Open-pore sintered glasses for use in electronic cigarettes

ABSTRACT

A sintered body for use as a liquid reservoir in an electronic cigarette, medication administering devices, in thermally heated evaporators for fragrant substances is provided. The sintered body is made of open-pore sintered glass and has a porosity of greater than 50 vol %. The average pore size is in a range from 1 to 450 μm. The glass of the sintered body has a transition temperature Tg of at least 450° C.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 15/893,584filed on Feb. 10, 2018, which is a continuation of InternationalApplication PCT/EP2016/068400 filed on Aug. 2, 2016, which claimsbenefit under 35 USC § 119 of German Application 10 2015 113 124.2 filedAug. 10, 2015, the entire contents of all of which are incorporatedherein by reference.

BACKGROUND 1. Field of the Invention

The invention generally relates to a liquid reservoir for hotapplications. In particular, the invention relates to a liquid reservoirfor storage and controlled release of evaporable substances for use inelectronic cigarettes, in medication administering devices, and/or inthermally heated evaporators for fragrant substances, and also relatesto an evaporator unit for evaporating liquids in electronic cigarettes,in medication administering devices, and/or in thermally heatedevaporators for fragrant substances.

2. Description of Related Art

Electronic cigarettes, also referred to as e-cigarettes below, areincreasingly being used as an alternative to tobacco cigarettes.Typically, electronic cigarettes comprise a mouthpiece and an evaporatorunit. The evaporator unit has a liquid reservoir which is connected to aheating element.

Certain medications, in particular medications for treating therespiratory tract, and/or the oral and/or nasal mucosa areadvantageously administered in evaporated form. Liquid reservoirsaccording to the invention can be used for storing and releasing suchmedications, in particular in administering devices for suchmedications. In this case, it is also possible that the liquid reservoiris connected to a heating element and thus forms at least part of anevaporator unit.

Thermally heatable evaporators are increasingly used to provide anambience with fragrant substances, in particular in bars, hotel lobbies,and/or vehicle interiors, such as the interiors of motor vehicles, inparticular automobiles. The evaporator unit used in this case also has aliquid reservoir connected to a heating element. The liquid reservoircontains a liquid which is usually a carrier liquid, such as propyleneglycol or glycerol, in which additives are dissolved and/or, moregenerally, contained, such as fragrant and flavoring substances, and/ornicotine, and/or medications. The carrier liquid is bonded on the innersurface of the liquid reservoir by adsorption processes.

Generally, the liquid stored in the liquid reservoir is evaporated bythe heating element, desorbed from the inner surface area of the liquidreservoir, and can be inhaled by the user. Here, temperatures of over200° C. are temporarily reached.

Thus, the liquid reservoir has to exhibit high uptake capability and ahigh adsorption effect, but at the same time, however, the liquid has tobe released rapidly at high temperatures.

From prior art, electronic cigarettes are known which have porous liquidreservoirs made of organic polymers. However, in case of excessiveheating power, for example if the liquid reservoir runs dry inuncontrolled manner, temperatures might be reached during operation atwhich volatile substances are released from the liquid reservoir ordecomposition of the liquid reservoir occurs. These substances mightthen be inhaled by the user.

Due to the low temperature stability of the polymeric material, it istherefore necessary to maintain a minimum spacing between the heatingelement and the liquid reservoir, which prevents a compact design of theevaporator unit and hence of the electronic cigarette.

As an alternative to maintaining a minimum spacing, a wick can be usedthat leads the liquid to be evaporated to the heating coil by capillaryforces. This wick is usually made of glass fibers. Although these glassfibers exhibit high temperature stability, the individual glass fiberstend to break easily, however. The same applies if the liquid reservoiritself is made of glass fibers. Therefore, there is a risk that the userinhales loosened or partially dissolved fiber fragments.

SUMMARY

An object of the invention is to provide a liquid reservoir for use inelectronic cigarettes and/or in medication administering devices and/orin thermally heated evaporators for fragrant substances, which does nothave the drawbacks described above. A further object of the invention isto provide an improved evaporator unit for hot applications forevaporating carrier liquids, in particular for an electronic cigarette,medication administering devices, and/or thermally heated evaporatorsfor fragrant substances.

The evaporator unit according to the invention for use in theaforementioned applications comprises a liquid reservoir and a heatingelement. A carrier liquid is stored in the liquid reservoir byadsorptive interactions, which carrier liquid may contain fragrant andflavoring substances and/or medications including active substancesand/or nicotine dissolved in suitable liquids, for example. By means ofthe heating element, high temperatures are generated in the evaporatorso that the carrier liquid is evaporated, desorbed from the innersurface area of the liquid reservoir, and the vapor can be inhaled bythe user.

The liquid reservoir according to the invention comprises a sinteredbody made of open-pore sintered glass. The liquid is stored in the openpores of the sintered body. The term “open-pore sintered body” refers inparticular to a sintered body in which at least 95% of the pore volumethereof are open pores.

The organic carrier liquid is adsorbed on the surface of the pores ofthe sintered body, i.e. on the inner surface area thereof. Preferably,in the loaded state prior to evaporation the weight of the carrierliquid in the liquid reservoir is at least 50% of the weight of thesintered body.

The carrier liquid is distinguished by good evaporability. Furthersubstances can be dissolved in the organic carrier liquid, in particularflavoring substances, fragrant substances, medications, and/or nicotine.In one embodiment of the invention, the nicotine concentration in thecarrier liquid is from 1 to 30 mg/ml, preferably from 2 to 20 mg/ml. Thecarrier liquid preferably contains propylene glycol, glycerol, andmixtures thereof as the main constituents.

The sintered body has a porosity of greater than 50 vol %, preferably ofat least 60 vol %, more preferably of at least 70 vol %. Due to the highporosity, high adsorption capacity of the sintered body is ensured.Thus, according to one embodiment, the sintered body can adsorbpropylene glycol in an amount of at least 50% of its weight at atemperature of 20° C. and in an adsorption time of 3 hours.

The average pore size of the sintered body is in a range from 1 to 450μm. This average pore size has been found to be particularlyadvantageous in terms of the adsorption capacity and the desorptionbehavior at room temperature, as well as at high temperatures in therange of the evaporation point of the carrier liquid, in particular attemperatures of about 300° C.

If the pores of the sintered body are too small, the latter cannot takeup sufficient carrier liquid. Although large pores are advantageous interms of adsorption capacity, they simultaneously cause a highdesorption rate at 20° C., i.e. under the storage conditions of a liquidreservoir for electronic cigarettes.

According to a refinement of the invention it is contemplated that thesintered body has a specific surface area of >0.5 m²/g or even >0.8m²/g. The large specific surface area is thereby responsible for a highadsorption capacity. However, under certain circumstances, an excessivespecific surface area may cause the carrier liquid to not be desorbedrapidly enough even at high temperatures, and/or may causechromatography effects to occur. Chromatography effects aredisadvantageous, because the various substances dissolved in the carrierliquid are desorbed at different times and thus the composition of thevapor will change during the operation of the aforementioned devices.Therefore, according to one embodiment of the invention, a specificsurface area of smaller than 20 m²/g or even smaller than 10 m²/g iscontemplated.

In addition to a high adsorption capacity, the sintered body in the formof a liquid reservoir has a low desorption rate at 20° C. Thus,according to one embodiment, not more than 15 wt % of the previouslyadsorbed liquid carrier medium, such as propylene glycol, is desorbedduring a desorption time of 100 hours, which is particularlyadvantageous in terms of long-term stability. At the same time, at least50% of the previously adsorbed mass of the liquid carrier medium, inparticular propylene glycol, is desorbed at a temperature of 300° C. anda desorption time of 5 minutes here.

Thus, the liquid reservoir is suitable for use in hot applications, inparticular in electronic cigarettes, and/or in medication administeringdevices, and/or in thermally heated evaporators for fragrant substances.

According to one embodiment of the invention, the average pore size isin a range from 5 to 400 μM. The average pore size may as well be in arange from 10 to 350 μm.

The sintered body may as well have a double pore structure. Here, adouble pore structure refers to macropores with a pore size from 20 to450 μm which have open microscopic pores in their pore walls, whichmostly have a size in a range from 1 to 10 μM.

The sintered body can be obtained by a method in which, first,fine-grained glass powder with grain sizes in a range of approximately20 μM to 600 μM, preferably a maximum of 300 μM, is mixed with ahigh-melting coarse-grained salt and a binder. 5 to 20 wt % offine-grained glass powder is added to this mixture, and the mass ispressed into shape. The resulting shaped body is heated to the sinteringtemperature of the glass and sintered. The melting temperature of theemployed glass is above the respective sintering temperature, so thatthe grain structure of the salt is preserved. After the sinteringprocess, the salt is washed out with a suitable solvent. The salts NaCland K₂SO₄ have been found to be particularly suitable for this purpose.Other salts such as KCl, MgSO₄, Li₂SO₄, Na₂SO₄ are conceivable as well.Besides such aspects as costs, environmental compatibility or the like,the choice of the salt is determined by the glass that is employed andthe temperature required for sintering same. According to one embodimentof the invention, 50 to 20 wt % of glass powder with a grain size from15 to 60 μm and an aqueous polyethylene glycol solution are added to 50to 80 wt % of salt with a grain size from 30 to 200 μM, and mixedthoroughly. The so obtained mixture can either be dried, or 5 to 20 wt %of glass powder (based on the mass of the mixture) can be added theretoin the moist state. The mixture is pressed into shape and sintered atthe sintering temperature of the employed glass. Subsequently, the saltis washed out so that a porous sintered body is obtained.

As a result, a highly porous sintered body with open pores is obtained.Since the individual glass grains are firmly bonded to each other by thesintering process, the sintered body has a good mechanical strengthcompared to a corresponding glass fiber material, despite of its highporosity. Thus, the sintered body does not contain any loose or easilyreleasable particles which might be inhaled by the user when thesintered body is used as a liquid reservoir in an electronic cigaretteand/or in a medication administering device and/or in thermally heatedevaporators for fragrant substances. Due to the high mechanicalstability of the sintered body, it is thus possible to provide liquidreservoirs which may even exhibit porosities of more than 80 vol %.

The sintered porous glass body is inert to carrier liquids as used inelectronic cigarettes, and/or in medication administering devices,and/or in thermally heated evaporators for fragrant substances. Also,the employed glass has a transition temperature T_(g) of at least 450°C. Due to the high transition temperature, the releasing behavior of theglass is very low, i.e. even at high temperatures glass constituents arenot released or only to a very limited extent. In addition, it ispossible to choose the composition of the glass so that it contains noor only very few volatile constituents.

In the case of an electronic cigarette, temperatures of significantlymore than 200° C. are reached in the evaporator in the area of theheating coil, locally up to 500 to 600° C. Due to the low releasingproperty of the employed glass, a liquid reservoir made of the sinteredbody according to the invention can thus be positioned substantiallycloser to the heating element than would be possible with a liquidreservoir made of a polymeric material, for example. This isadvantageous in terms of the design options of electronic cigarettes.For example, the electronic cigarette may have a more compact design, orthe additional space available within the electronic cigarette may beused for other functions. According to one embodiment of the invention,the glass has a transition temperature T_(g) of greater than 500° C. oreven greater than 600° C. In one embodiment of the invention, the glassof the sintered body has transition temperatures of more than 700° C.The same applies to medication administering devices and/or to thermallyheated evaporators for fragrant substances.

Glasses containing SiO₂ have been found to be particularly advantageous.Borosilicate glasses, aluminosilicate glasses, aluminoborosilicateglasses, or soda-lime glasses have proved to be particularly suitable.

According to one embodiment of the invention, the glass of the sinteredbody contains the following constituents (in wt % on an oxide basis):

SiO₂ 70 to 75 wt %; Na₂O + K₂O 12 to 16 wt %; CaO 8 to 11 wt %; MgO 0 to5 wt %; and Al₂O₃ 0 to 2 wt %.

According to a further embodiment of the invention, the glass containsthe following constituents (in wt % on an oxide basis):

SiO₂ 70 to 85 wt %; B₂O₃ 5 to 15 wt %; Alkali oxides 3 to 7 wt %;Alkaline earth oxides 0 to 4 wt %; and Al₂O₃ 2 to 5 wt %.

Glasses containing the following constituents have also proven to beadvantageous:

SiO₂ 55 to 75 wt %; Na₂O 0 to 15 wt %; K₂O 2 to 14 wt %; Al₂O₃ 0 to 15wt %; MgO 0 to 4 wt %; CaO 3 to 12 wt %; BaO 0 to 15 wt %; ZnO 0 to 5 wt%; and TiO₂ 0 to 2 wt %.

According to a further embodiment of the invention, the glass containsthe following constituents:

SiO₂ 30 to 85 wt %; B₂O₃ 0.5 to 20 wt %; Al₂O₃ 0 to 15 wt %; Na₂O 3 to15 wt %; K₂O 2.5 to 15 wt %; ZnO 0 to 12 wt %; MgO 2 to 10 wt %; BaO 0to 10 wt %; TiO₂ 0 to 10 wt %; and CaO 0 to 8 wt %, preferably max. 5 wt%.

According to one embodiment, the glass is an aluminosilicate glasscontaining the following constituents:

SiO₂ 58 to 65 wt %; B₂O₃ 6 to 10.5 wt %; Al₂O₃ 14 to 25 wt %; MgO 0 to 5wt %; CaO 0 to 9 wt %; BaO 0 to 8 wt %; SrO 0 to 8 wt %; ZnO 0 to 2 wt%; and with Σ(MgO + CaO + BaO) 8 to 18 wt %.

According to another embodiment, the glass contains the followingconstituents:

SiO₂ 50 to 60 wt %; B₂O₃ 8 to 12 wt %; Al₂O₃ 8 to 12 wt %; and BaO 20 to30 wt %.

According to one embodiment, the glass contains the followingconstituents:

SiO₂ 75 to 85 wt %; B₂O₃ 8 to 18 wt %; Al₂O₃ 0.5 to 4.5 wt %; Na₂O 1.5to 5.5 wt %; and K₂O 0 to 2 wt %.

Furthermore, the glass exhibits high thermal resistance. According toone embodiment of the invention, it is contemplated that the glass has acoefficient of linear thermal expansion α_(20-300° c.) in a range from2.5 ppm/K to 10.5 ppm/K, preferably in a range from 3.0 ppm/K to 10.0ppm/K. As a result, the sintered body also exhibits high thermal shockresistance. In this respect, sintered bodies with thermal expansioncoefficients of up to a maximum of 9.5 ppm/K have been found to beadvantageous.

Due to the high transition temperatures of the glass used for thesintered body and its high temperature resistance, the heating elementcan be mounted close to the liquid reservoir in the evaporator, whichallows for a compact design of the electronic cigarette and/or ofmedication administering devices and/or of thermally heated evaporatorsfor fragrant substances.

Based on the fabrication process it is possible to adapt the form of thesintered body and hence also that of the liquid reservoir to any desiredshape, which makes it possible to combine several functionalities in asingle component. According to one embodiment of the invention, thefunctions of the liquid reservoir, a wick, an air suction passage, andthe heating element can be implemented in a single component of theevaporator, which makes it possible to exactly adjust the heating powerand thus to achieve improved temperature control.

In a further embodiment of the invention, the heating element isdirectly applied on the liquid reservoir. It can be applied on thesurface of the liquid reservoir in the form of a metal foil or a metalwire, for example. According to another embodiment, the heating elementis applied on the liquid reservoir as a metallic coating. The directarrangement of the heating element on the sintered body is advantageous,since less energy is required if the heating element is applied directlyon the liquid reservoir, which reduces battery consumption of theelectronic cigarette. In addition, better temperature control can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail by way of exemplaryembodiments and FIGS. 1a to 9, wherein:

FIGS. 1a and 1b are SEM images of one embodiment of the sintered bodyaccording to the invention;

FIGS. 2a and 2b are SEM images of sintered glasses with different poresizes as comparative examples;

FIGS. 3a and 3b are SEM images of sintered glasses with different poresizes as comparative examples;

FIG. 4 is an SEM image of a liquid reservoir made of an organicpolymeric material as a second comparative example;

FIG. 5 is a graphical diagram showing the adsorption capacity of theexemplary embodiment and various comparative examples;

FIG. 6 is a graphical diagram of the desorption of one embodiment of aliquid reservoir according to the invention and a polymeric comparativeexample at 20° C.;

FIG. 7 is a graphical diagram of the desorption of one embodiment of aliquid reservoir according to the invention and the comparative examplesat 300° C.;

FIG. 8 is a schematic view of the configuration of an electroniccigarette; and

FIG. 9 is a schematic view of the configuration of one embodiment of theevaporator unit in which the heating element is directly arranged on theliquid reservoir.

DETAILED DESCRIPTION

Table 1 shows six different exemplary embodiments of a sintered bodyaccording to the invention. The individual exemplary embodiments differin terms of the composition of the sintered glass.

TABLE 1 COMPOSITION AND PROPERTIES OF EXAMPLES 1 TO 6 Composition Exam-Exam- Exam- Exam- Exam- Exam- [wt %] ple 1 ple 2 ple 3 ple 4 ple 5 ple 6SiO₂ 69 80 61 55 72.8 74.3 B₂O₃ 1 13 10 10 Al₂O₃ 4 2.5 18 10 0.2 1.3Na₂O 13 3.5 13.9 13.2 K₂O 3 1 0.1 0.3 BaO 2 3.3 25 CaO 5 4.8 9.0 10.7MgO 3 2.8 4.0 0.2 α₍₂₀₋₃₀₀₎ 9.1 3.25 3.2 4.0 9.5 9.0 [ppm/K] Density 2.52.2 2.43 2.80 [g/cm³] Tg [° C.] 525 525 717 665 564 573

FIGS. 1a and 1b are SEM images (scanning electron micrographs) of anexemplary embodiment of the sintered body. The sintered body exhibits avery porous structure, both at the surface and at the breaking edge.Pores 1 are between 90 and 330 μm in size. In addition to the large openpores, the sintered body also has very small closed pores 2. Forproducing the exemplary embodiment of FIG. 1, NaCl was used as a salt.

FIGS. 2a to 3b are SEM images of two different porous sintered glasseswith different pore sizes. FIGS. 2a and 2b show SEM images of a poroussintered glass which has a multitude of very small pores. Pores 3 areonly a few nanometers in size. The sintered glass of FIGS. 3a and 3bconsists of many relatively large sintered glass grains 4. Theintermediate spaces 5 between the individual glass grains 4 are verylarge here.

FIG. 4 shows an SEM image of a liquid reservoir made of an organicpolymer. The storage medium consists of entangled polymeric fibers 6.Thus, the liquid reservoir has a nonwoven structure. Between theindividual fibers 6 there are many cavities 7 which can take up acarrier liquid.

FIG. 5 illustrates the uptake capacity of liquid reservoirs. For thispurpose, the different liquid reservoirs were soaked in propylene glycolfor 3 hours, and then the mass increase was determined. Exemplaryembodiment 10 corresponds to the sintered glass shown in FIG. 1.Comparative example 11 is the sintered glass of FIG. 3 with the pores ofonly a few nanometers in size. Comparative example 8 is the polymericnonwoven of FIG. 4. Comparative example 9 is a sintered ceramic.Comparative example 12 has very large pores.

It will be apparent from FIG. 5, that a ceramic structure 9 can onlytake up a small amount of propylene glycol and is therefore not suitableas a liquid reservoir for use in electronic cigarettes and/or inmedication administering devices and/or in thermally heated evaporatorsfor fragrant substances.

In sintered glasses, uptake capacity depends on the pore size. Sinteredglasses with very small pores 11 cannot take up enough propylene glycol,whereas in sintered glasses with excessively large pores 12 the specificsurface area is too small to fully adsorb the uptaken propylene glycol.Therefore, a large proportion of the uptaken propylene glycol will flowsout of the pores again. By contrast, the pores of exemplary embodiment10 are large enough to take up enough propylene glycol and small enoughto provide a sufficiently large specific surface area on which thepropylene glycol can be adsorbed.

In addition to exemplary embodiment 10, the liquid reservoir ofpolymeric material 8 also exhibits high uptake capacity.

FIG. 6 illustrates the results of a desorption test at 20° C. for theexemplary embodiment 10 and the polymeric liquid reservoir 8. For thispurpose, the samples 8 and 10 soaked with propylene glycol were storedat a temperature of 20° C., and the mass loss of propylene glycol wasmeasured as a function of time. Even after a period of 5 days, both theexemplary embodiment and the polymeric liquid reservoir show a loss ofpropylene glycol of less than 20 wt % of the previously uptakenpropylene glycol.

FIG. 7 illustrates desorption of propylene glycol at 300° C. For thispurpose, the samples 8 to 12 were first soaked with propylene glycol andthen dried at 300° C. in a furnace for 5, 10, 20, and 40 minutes. Themass loss of propylene glycol was determined with a balance. After 10minutes, all samples had released the major proportion of propyleneglycol. In exemplary embodiment 10, 50% of the propylene glycol hadevaporated already after 5 minutes. While the polymeric sample 8 hadmelted as soon as after 5 minutes at 300° C., the exemplary embodimentwithstands the high temperature load.

It will be obvious from FIGS. 5 to 7 that the liquid reservoir accordingto the invention is outstandingly suitable for use in an electroniccigarette and/or in medication administering devices and/or thermallyheated evaporators for fragrant substances.

The underlying adsorption and desorption tests shown here are exemplary.Alternative determinations of the uptake and release capacity aremanifold, e.g. quantitative tracking of coloring/discoloring of a bodyin contact with dyed propylene glycol.

FIG. 8 illustrates an electronic cigarette 21 according to theinvention. Cigarette 21 comprises a tip 23 and a mouthpiece 25 on whichthe user drags to inhale the aerosol generated in the cigarette by meansof an evaporator 22. According to a preferred embodiment of theinvention, mouthpiece 25 is removable from tip 23.

Cigarette 21 comprises an electrical energy storage 27 in order toprovide the electrical energy for evaporating the organic liquid inevaporator 22. In the illustrated embodiment, the electrical energystorage 27 is accommodated in the tip 23 of cigarette 21. Medicationadministering devices may have a similar configuration.

Electronic cigarette 21 further comprises a control unit 31 whichcontrols the heating power for evaporator 22. In particular, the controlunit 31 may be configured to check whether a user is inhaling and,depending thereon, to regulate the heating power of evaporator 22.Furthermore, a light-emitting diode 29 may be disposed in the tip 23,which is also controlled by control unit 31. When the control unit 31detects that the user is dragging on cigarette 21, it can control thelight-emitting diode 29 so that the light-emitting diode 29 lights up.Thus, a visual effect is achieved corresponding to the glowing whendragging on a conventional cigarette.

The evaporator unit 22 according to the invention includes a liquidreservoir 24 comprising a sintered body 28 and organic carrier liquid 10adsorbed in the sintered body 28. The sintered body 28 has a specificsurface area preferably in a range from 0.5 square meters per gram to amaximum of 10 square meters per gram. A specific surface area in thisrange leads to a high uptake capacity for carrier liquid 30 and at thesame time still sufficient mechanical and thermal stability.

For heating the liquid reservoir 24 and thus for evaporating the organiccarrier liquid 30 with constituents dissolved therein, such as nicotine,fragrant substances, and/or flavoring substances, the evaporator unit 22comprises an electrically heatable heating element 26. Heating element26 is supplied with power by electrical energy storage 27, controlled bycontrol unit 31. By heating to an operating temperature of greater than100° C., the organic carrier liquid 30 adsorbed in the sintered body 28,in particular a high-boiling alcohol such as glycerol or propyleneglycol, can be evaporated. The sintered body 28 has a porosity of morethan 50 vol % in order to be able to take up a large amount of carrierliquid and to be able to release the carrier liquid with the dissolvedflavoring substances and/or stimulants, such as in particular nicotine,over a sufficiently long time.

The glass used for the sintered body 28 preferably has a coefficient oflinear thermal expansion α in a range from 2.5 ppm/K (i.e. 2.5·10⁻⁶ K⁻¹)to 10.5 ppm/K, preferably in a range from 3.0 ppm/K to 10.0 ppm/K.Transition temperatures T_(g) of greater than 450° C., in particulargreater than 500° C. are particularly preferred. Suitable glasses aredisclosed herein.

FIG. 9 shows an exemplary embodiment of an evaporator unit 22 in whichthe heating element 26 is disposed directly on the sintered body 28. Inparticular, the heating element 26 is firmly connected to the sinteredbody 28. Such a connection can in particular be achieved if the heatingelement 26 is provided in the form of a sheet resistor. For thispurpose, an electrically conductive sheet resistor type coatingpatterned in the form of a conductive path is applied onto the sinteredbody 28. A coating that is directly applied to the sintered body 28 as aheating element 26 is advantageous in order to achieve good thermalcontact which provides for fast heating, inter alia. In the presentillustrated example, enlarged contacts 261, 262 are provided in theconductive coating, at which the sheet resistor can be electricallycontacted. The electrical connection can be established to matingcontacts in the mouthpiece 25 when the liquid reservoir 24 is inserted,for example.

What is claimed is:
 1. A liquid reservoir, comprising: a sintered bodyincluding an open-pore sintered glass with a porosity of >50 vol % andan average pore size in a range from 1 to 450 μm, wherein the open-poresintered glass comprises glass having a transition temperature of atleast 450° C.; and an organic carrier liquid adsorbed by the sinteredbody.
 2. The liquid reservoir as claimed in claim 1, wherein the organiccarrier liquid has a volume that is at least 50 wt % of a weight of thesintered body.
 3. The liquid reservoir as claimed in claim 1, whereinthe organic carrier liquid comprises at least one of alcohol, propyleneglycol, and glycerol.
 4. The liquid reservoir as claimed in claim 1,wherein the organic carrier liquid comprises at least one of nicotine, afragrant substance, and a flavoring substance dissolved therein.
 5. Theliquid reservoir as claimed in claim 1, wherein the organic carrierliquid comprises nicotine in an organic solvent, the nicotine having aconcentration in the solvent from 1 to 30 mg/ml.
 6. The liquid reservoiras claimed in claim 1, wherein the sintered body is a one-piece shapedpart.
 7. The liquid reservoir as claimed in claim 1, wherein theopen-pore sintered glass has a mass, and wherein the organic carrierliquid is propylene glycol, the open-pore sintered glass adsorbingpropylene glycol in an amount of at least 50% of the mass at atemperature of 20° C. and in an adsorption time of 3 hours.
 8. Theliquid reservoir as claimed in claim 7, wherein the open-pore sinteredglass is configured so that not more than 15 wt % of previously adsorbedpropylene glycol is desorbed during a desorption time of 100 hours, andwherein the open-pore sintered glass desorbs at least 50% of thepreviously adsorbed propylene glycol at a temperature of 300° C. and adesorption time of 5 minutes.
 9. The liquid reservoir as claimed inclaim 1, wherein the glass has a coefficient of linear thermal expansionα in a range from 2.5 ppm/K to 10.5 ppm/K.
 10. The liquid reservoir asclaimed in claim 1, wherein the average pore size is in a range from 10μm to 350 μm.
 11. The liquid reservoir as claimed in claim 1, whereinthe porosity is at greater than 80 vol %.
 12. The liquid reservoir asclaimed in claim 1, wherein the glass is selected from the groupconsisting of a borosilicate glass, an aluminosilicate glass, analuminoborosilicate glass, and a soda-lime glass.
 13. The liquidreservoir as claimed in claim 1, wherein the glass comprises (in wt % onan oxide basis): SiO₂ 70 to 75 wt %; Na₂O+K₂O 12 to 16 wt %; CaO 8 to 11wt %; MgO 0 to 5 wt %; and Al₂O₃ 0 to 2 w %.
 14. The liquid reservoir asclaimed claim 1, wherein the glass comprises (in wt % on an oxidebasis): SiO₂ 70 to 85 wt %; B₂O₃ 5 to 15 wt %; Alkali oxides 3 to 7 wt%; Alkaline earth oxides 0 to 4 wt %; and Al₂O₃ 2 to 5 wt %.


15. The liquid reservoir as claimed in claim 1, wherein the glasscomprises (in wt % on an oxide basis): SiO₂ 50 to 75 wt %; Na₂O 0 to 15wt %; K₂O 2 to 14 wt %; Al₂O₃ 0 to 15 wt %; MgO 0 to 4 wt %; CaO 3 to 12wt %; BaO 0 to 15 wt %; ZnO 0 to 5 wt %; and TiO₂ 0 to 2 wt %.


16. The liquid reservoir as claimed in claim 1, wherein the glasscomprises (in wt % on an oxide basis): SiO₂ 30 to 85 wt %; B₂O₃ 0.5 to20 wt %; Al₂O₃ 0 to 15 wt %; Na₂O 3 to 15 wt %; K₂O 2.5 to 15 wt %; ZnO0 to 12 wt %; MgO 2 to 10 wt %; BaO 0 to 10 wt %; TiO₂ 0 to 10 wt %; andCaO 0 to 8 wt %.


17. The liquid reservoir as claimed in claim 1, wherein the glasscomprises (in wt % on an oxide basis): SiO₂ 50 to 60 wt %; B₂O₃ 8 to 12wt %; Al₂O₃ 8 to 12 wt %; and BaO 20 to 30 wt %.


18. The liquid reservoir as claimed in claim 1, wherein the glasscomprises (in wt % on an oxide basis): SiO₂ 75 to 85 wt %; B₂O₃ 8 to 18wt %; Al₂O₃ 0.5 to 4.5 wt %; Na₂O 1.5 to 5.5 wt %; and K₂O 0 to 2 wt %.


19. The liquid reservoir as claimed in claim 1, wherein the glasscomprises (in wt % on an oxide basis): SiO₂ 58 to 65 wt %; B₂O₃ 6 to10.5 wt %; Al₂O₃ 14 to 25 wt %; MgO 0 to 5 wt %; CaO 0 to 9 wt %; BaO 0to 8 wt %; SrO 0 to 8 wt %; ZnO 0 to 2 wt %; and a total of MgO, CaO,and BaO is 8 to 18 wt %.


20. An evaporator unit, comprising: a sintered body as a liquidreservoir, the sintered body including an open-pore sintered glass witha porosity of >50 vol % and an average pore size in a range from 1 to450 μm, wherein the open-pore sintered glass comprises glass having atransition temperature of at least 450° C.; and a heating element. 21.The evaporator unit as claimed in claim 20, wherein the heating elementis directly disposed on the sintered body.
 22. The evaporator unit asclaimed in claim 20, wherein the heating element comprises a deviceselected from the group consisting of a metal foil, a metal wire, and anelectrically conductive coating.
 23. The evaporator unit as claimed inclaim 20, wherein the evaporator unit is configured for use as anelectronic cigarette.
 24. The evaporator unit as claimed in claim 20,wherein the evaporator unit is configured for use as a medicationadministering device.
 25. The evaporator unit as claimed in claim 20,wherein the evaporator unit is configured for use as a thermally heatedevaporator for fragrant substances.